1. Field of the Invention
The present invention relates to systems and methods for accurate placement of components in or on assemblies, and in particular, to a system and method for augmenting a positioning system to precisely determine component locations in otherwise inaccessible areas.
2. Description of the Related Art
The production of large assemblies often requires precise placement of related components and subsystems. This can be accomplished with computer aided measurement systems (CAMS) that can survey and record point coordinates on the exterior or interior of an aircraft to generate a three-dimensional (3D) map of the assembly that can be compared to design specifications, especially those prepared by computer-aided design (CAD) techniques. Using such maps and a portable hand-held remote device, the precise spatial location for related components and subsystems can be determined by using the CAMS and the 3D map to direct the placement of the device, and hence, the desired location of the component.
Typically, CAMS include an illumination device such as a laser, a reflective object for reflecting the illumination, a receiver for receiving the reflective light, and a computer. The CAMS may be implemented by a LIDAR (light detection and ranging) system in which the illuminator rapidly scans the area of interest, and determines the spatial location of the reflective (and typically spherical) object using reflected energy received from the object. Typically, the reflective object is spherical, allowing the center of the reflective object to be easily determined. That is, the attitude of the reflective object is of no concern, as a light beam from the illuminator and the light beam reflected from the spherical object are substantially co-linear.
The CAMS may also be implemented by a laser tracker and a retro-reflector. Unlike the LIDAR system, the illuminator does not repeatedly scan the area of interest. Instead, using received reflected energy, the illuminator tracks the reflective object as it is moved around.
One advantage of such LIDAR systems is that they can easily reacquire track of objects that have passed through an area that is in the shadow of the illuminator, while laser tracking systems cannot readily reacquire track.
In both LIDAR and laser-tracker systems, the computer controls the laser to illuminate the reflector, and the receiver senses energy reflected from the illuminated reflective object. Since the computer is aware of the angular displacement of the illuminator and the time it takes for the light beam to bounce off of the reflector and return to the receiver, and can determine the spatial position and range of the features from the reflected energy. Since the reflective object can be placed against features of interest, the assembly can be precisely mapped.
However, this technique is limited to situations where there is a line of sight between the feature and the illumination device. Such systems are currently incapable of providing any information regarding placement in locations where the structure can not be illuminated (e.g. not in the line of sight of the illumination device and the receiver). Hence, the practicality of continuous and/or autonomous position awareness remains poor.
What is needed is a system and method for precise measurement and placement of components and systems on assemblies, even in places where such placement is at a location that is not illuminable by the illumination device of the CAMS. The present invention satisfies that need.